Core shooting method and core shooting apparatus for the production of cores with simultaneous curing process

ABSTRACT

A core shooting method includes:
     a. Inserting a first core shooting tool into a core shooting machine;   b. Injecting core molding material and a binder into the first core shooting tool;   c. Ejecting the first core shooting tool from the core shooting machine;   d. Curing of the core in the first core shooting tool;   e. Repeating the previous steps with at least one further core shooting tool, wherein the insertion of the further core shooting tool into the core shooting machine is carried out simultaneously with the ejection of the previous core shooting tool from the core shooting machine or simultaneously with the curing of the core in the previous core shooting tool.   

     A corresponding core shooting tool is further described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/DE2020/100993, filed on Nov. 24, 2020, which claims the benefit of German Patent Application No. 10 2019 134 739.4, filed on Dec. 17, 2019. The entire disclosures of the above applications are incorporated herein by reference.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

TECHNICAL FIELD

The invention relates to a core shooting method with a plurality of core shooting tools, each of which has at least two tool contour shells or tool halves which are adjustable between an open position and a closed position, the core shooting tools in the closed position each forming a hollow chamber geometrically adapted to a core to be shot. A core shooting method is known, for example, from U.S. Pat. No. 7,588,070 B2. A similar core shooting method is also known from FR 3 047 429 A1. Other devices and methods for manufacturing cores are described in DE 10 2012 019181 A1, SU 1759525 A2, U.S. Pat. No. 4,158,381 A and DE 32 21 357 A1, respectively, and in JP 2006 01948 A and JP H03 258439 A.

DISCUSSION

In order to cast complex components or molded parts, cores are often required which can be inserted into molds, for example to form cavities in the component or molded part. Such cores can be produced with core shooting tools. In this process, a core molding material consisting of sand and a binder is usually injected into the core shooting tool. In the process, the core molding material takes the shape of the hollow chamber enclosed by the tool and can then be cured. To cure the core material, the core can be gassed or flowed through with a gas, for example. Alternatively, it is possible to cure the core by applying heat, in particular by heating the core shooting tool.

The processes known from the prior art have the disadvantage that the cores remain in the core shooting tool for hardening within the core shooting machines, which means that high cycle times must be taken into account for the series production of cores. The core must be “baked” in the mold until it has a sufficiently thick wall. Another disadvantage is that high curing temperatures are required to reduce the cycle times, but this increases mold wear.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

It is therefore one aspect of the invention to provide a core shooting method that enables series production of cores with reduced cycle times.

Accordingly, a core shooting method is proposed using a plurality of core shooting tools, each of which is adjustable between an open position and a closed position, wherein in the closed position the core shooting tools each form a hollow chamber geometrically adapted to a core to be shot, the method comprising the sequence of steps:

Insertion of a first core shooting tool into a core shooting machine;

Introduction of core molding material and a binder into the first core shooting tool;

Ejecting the first core shooting tool from the core shooting machine;

Curing of the core in the first core shooting tool, wherein for curing the core in the core shooting tool, the core shooting tool is transferred to an infrared furnace;

Repeating the previous steps with at least one further core shooting tool, wherein insertion of the further core shooting tool into the core shooting machine is carried out simultaneously with ejection of the previous core shooting tool from the core shooting machine or simultaneously with curing of the core in the previous core shooting tool.

It is further provided that inserting a first core shooting tool into a core shooting machine comprises inserting two tool contour shells having a wall thickness of less than 20 mm.

The main advantage of the invention is that by using a plurality of core shooting tools and ejecting core shooting tools already filled with core molding material from the core shooting machine, on the one hand one does not have to rely on only one core shooting tool but can already prepare further core shooting tools for the shooting method simultaneously while the first core shooting tool is still in the machine. On the other hand, the fact that the hardening process is removed from the machine and relocated to a hardening furnace represents a major time-saving potential. At the same time, accepting longer curing times by lowering the curing temperature can reduce the load on the individual tools or allow the use of environmentally friendly inorganic binder. Worn tools can also be successively replaced by new tools, so that intact core shooting tools are always available and machine downtimes can be minimized.

In this regard, prior to the introduction of core molding material and a binder into the first core shooting tool, binder may be pre-applied to the interior surfaces of the hollow chamber.

It may be envisaged that the insertion of a first core shooting tool into a core shooting machine comprises the insertion of two tool contour shells and bringing their locking into a closed position by means of a toggle device.

In particular, it may be provided that injecting core molding material and a binder into the first core shooting tool comprises: Injecting core molding material into the first core shooting tool and injecting binder into the injected core molding material. This may be done, for example, via an injection device having a plurality of injection nozzles which, after core molding material is injected into the cavity of the core shooting tool, is inserted through corresponding openings in one of the tool contour shells to inject binder into the molding material at that position. For example, the introduction of the binder of the injection device can be performed through the vent nozzles of the core shooting tool. Alternatively, a device for introducing the binder via the vapor or gas phase may be provided.

It may be further provided that introducing core molding material and a binder into the first core shooting tool comprises: Injecting a core molding material-binder mixture into the core shooting tool. In particular, this can be done via a metering pump operating according to the endless piston principle, whereby admixing of the binder to the core molding material can only take place in the nozzle tip.

By transferring the core shooting tool to a curing furnace, in particular an infrared furnace, to cure the core in the core shooting tool, the core shooting tool can be left in the furnace until the binder has cured to such an extent that it can be removed. Preferably, the tool is heated in an oven until a stable shell has formed. Alternatively, the core shooting tool can be heated with flames or heated inductively. If a cement binder is used, the humidity in the furnace can be maintained at a high level. Preferably, the furnace may have a recirculating air device to circulate the humidity.

Alternatively, the process can also be carried out using gas curing. For this purpose, the mold can be placed in a gas-tight chamber after shooting instead of in a furnace. There, the mold is flushed with CO₂ or an amine gas, for example, until the gas has penetrated the entire core. The mold can then be removed from the gas-tight chamber and opened so that the cured core can be removed.

It is also conceivable that the process is a shell molding or crowning process. In this case, a binder-coated core molding material can be injected into the core shooting tool mold. Subsequently, the mold can be heated in a furnace until a stable shell has formed, whereby the furnace for rapid heating can be, for example, an infrared furnace; alternatively, the core shooting mold can be heated with flames or inductively heated. In particular, loose material can be emptied from the core to improve gas permeability.

Alternatively, it may be envisaged that the process is carried out with cold-curing binders such as slowed furan resins, cement binders or gypsum binders. In this case, after the core has been shot, the mold can be placed in a furnace and left there at a moderate temperature until the binder has cured sufficiently for removal to take place. In the case of cement binder, the humidity in the furnace can be kept at a high level.

In addition, the process can be a cold box process. A particular advantage of a cold box process is the possibility of using lighter tools compared to hot box processes. Furthermore, lower process temperatures can result in less wear and a significant cost advantage over hot box processes. It is also conceivable for the process to be carried out as a hot-box process with inorganic or other heat-curing binder systems.

In addition, the binder may be an inorganic binder. The advantage of inorganic binders is that they are more environmentally friendly than organic binders and produce less smoke during casting. This reduces the impact on employees due to lower odor development and prevents condensate deposits on the casting tools.

It may be provided that the curing temperature during curing of the core is less than or equal to 110° C., preferably less than or equal to 100°, particularly preferably less than or equal to 90° C. On the one hand, this allows the use of an inorganic binder and, on the other hand, the use of mold shells made of plastic or lower mold wear.

In particular, it may be provided that the core shooting tool is opened after the core has cured and the cured core is removed.

In addition, it is possible to clean the core shooting tool after removal of the core, reset it to a shootable state, and then reinsert it into the core shooting machine. The fact that cleaning takes place “offline” means that the duration of this production step can also be deducted from the cycle time. Outsourcing as many functions as possible from the core shooting tool also has the advantage that the functional scope of the core shooting tool is reduced and it is basically reduced to a simple sand conveying device. Furthermore, by removing the mold from the machine on a regular basis, the mold condition can be checked at regular intervals so that the mold condition is basically better. As a result, cores can be shot at lower pressures, which in turn has a beneficial effect on tool wear and energy consumption. In addition, individual failures of core shooting tools do not lead to a failure of the entire plant. In addition, quality assurance measures are easier to perform. It may be envisaged that cleaning of the core shooting tools takes place at a cleaning station. In particular, cleaning of the shot nozzles and/or cleaning of the shaping surfaces and/or cleaning of the connecting, sealing and contact surfaces can be carried out.

In addition, the same geometrically adapted hollow chamber can be formed in each of the plurality of core shooting tools. By using the same mold shells, time-consuming changeover operations between the individual core shooting methods can be avoided. The curing of the cores is also allowed to take more time while maintaining the low cycle time due to the many identical mold shells available. This redundancy due to several identical core shooting tools thus makes it possible to outsource the time-intensive steps that do not necessarily have to be performed within the machine, such as curing, core removal, cleaning and returning to a shootable state.

Furthermore, a core shooting tool for carrying out the core shooting method is disclosed, having a first tool contour shell and a second tool contour shell which can be moved back and forth between a closed position and an open position, wherein in the closed position a hollow chamber geometrically adapted to a core to be shot is formed in the core shooting tool, with at least one shot hole for introducing core molding material and/or binder into the hollow chamber, and with at least one frame for moving the core shooting tool into and out of the core shooting machine, the frame having at least one horizontally and/or vertically supporting support element for absorbing forces acting on the tool contour shells.

For this purpose, at least one closing element for automated closing can be provided, in particular at least two closing clamps, which holds the mold contour shells in the closed position. The closing clamps can be designed in particular as C-profiles which grip around the lower and upper mold contour shells and generate a predetermined pretension. The C-profiles can be guided by rails and designed to be laterally adjustable. Furthermore, the C-profiles can be height-adjustable via hydraulics, so that the profile width can be adjusted via this. The closing element can also be designed as a toggle closing element mounted on the core shooting tool. Alternatively, the mold contour shells can be screwed together.

It may be provided that the tool contour shells each have a wall thickness of less than 20 mm, preferably less than 10 mm, particularly preferably less than 5 mm. The use of thin tool contour shells is particularly advantageous in terms of material consumption. Thin mold contour shells also have the advantage that the core accommodated in the shells can be brought to the predetermined curing temperature in the curing furnace more quickly and with less energy input.

In particular, the mold contour shells can be formed essentially from plastic. So-called “casting copying processes” can be used to manufacture the tools. The advantage of plastic in particular is that it is cheaper to produce and requires less energy. Furthermore, handling is simplified because the tool contour shells have a lower weight. The plastic may, for example, comprise a polymer. The polymer may be, for example, a thermoplastic or a thermoset. The thermoplastic may comprise one or more of the following group: Polyamide, Polyoxymethylene, Polypropylene, Polyethylene, Acrylonitrile butadiene styrene, Polyphenylene sulfide, Polysulfone, Polymethyl methacrylate, Polystyrene, Polycarbonate, Polycarbonate/acrylonitrile butadiene styrene, Poly ether ether ketone, Poly ether acryl ketone, Polytetrafluorethylene. The thermoset may have one or more of the following group: Polyurethane, Cast polyamide, Epoxy resin, Melamine resin, Urea resin, Phenolic resin, Furan resin.

In addition, a venting nozzle can be provided on at least one of the mold contour shells. Alternatively, the tools can be vented via several nozzles, since there is no need for explicit exhaust ducts. On the one hand, the core shooting tool mold can be vented via the venting nozzles. In addition, it is conceivable that the binder is introduced via the vent nozzles. Alternatively, special access nozzles can also be provided, via which the binder is introduced into the core shooting tool. A further alternative is that the binder is introduced via the shot hole. The binder can be introduced into the core shooting tool as an aerosol, in gaseous form or in its vapor phase.

Alternatively, the mold contour shells can be porous or perforated. With such mold contour shells, the binder can be introduced by a dipping process.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

Exemplary embodiments of the invention are explained with reference to the following figures. Thereby shows:

FIG. 1 an example of a casting to be produced;

FIG. 2 an embodiment of a lower mold contour shell;

FIG. 3 an example of a core shooting tool clamped in the closed position by means of a clamp;

FIG. 4 a core shooting process in a core shooting tool provided with a clamp (not shown);

FIG. 5 heating of the shot and clamped core shooting tool in a curing furnace;

FIG. 6 an exemplary circulation system using a plurality of core shooting tools;

FIG. 7 a an example of an embodiment in which a binder is applied to the inner surfaces of the mold contour shells;

FIG. 7 b the embodiment example according to FIG. 7 a , in which, after the binder has been placed in front of the core, binderless sand is poured into the core shooting tool;

FIG. 8 a a further embodiment in which, after the sand has been introduced, the binder is introduced into the sand via venting nozzles in the lower mold contour shell;

FIG. 8 b the embodiment example according to FIG. 8 a , in which the injector system introduces binder into the sand via the deaeration nozzles;

FIG. 9 an example of a core shooting tool with a side shift.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

FIG. 1 shows an example of a sand core to be used for a casting 16, which corresponds to the negative of a section of the inner contour of the casting The casting of liquid metal into a mold results in a solid casting 16 without the use of cores. If, however, the casting 16 is to be hollow for reasons of an intricate geometric design, for example to save weight or to allow media to pass through, there are various methods of achieving this by means of cores produced by the core shooting method. In this process, the shape of the cavity to be created is made with specially prepared molding material. This sand core is then placed inside the mold at the location where the cavity or an undercut is to be created. If necessary, this core can be reinforced with core irons so that it is not destroyed during the casting process.

FIG. 2 shows a lower mold contour shell 3 which represents the lower half of the contour of the sand core from FIG. 1 . The lower tool contour shell 3 has at least sections of flat bearing surfaces on its underside, its upper side and on the side walls, so that it can be easily placed and moved in the core shooting machine, or that the upper tool contour shell 2 can be placed on the lower tool contour shell 3 in a particularly simple manner, or that unproblematic fastening of the fastening clamps 5 for bracing both tool contour shells 2, 3 against each other is made possible.

A core shooting tool 1 with both tool contour shells 2, 3 in their closed position is shown in FIG. 3 . The tool contour shells 2, 3 are placed on top of each other in such a way that a cavity 4 geometrically adapted to the sand core to be produced is formed inside them. Preferably, the contact surfaces of the contour shells 2, 3 can be designed in such a way that they have a self-centering function and the contour shells 2, 3 are thus automatically correctly aligned with each other. For example, the contact surfaces of both tool contour shells 2, 3 can be angled in a complementary manner to each other. For example, the contact surface of the lower mold contour shell 3 can be angled circumferentially in the shape of a loop or funnel, and the contact surface of the upper mold contour shell 2 can be designed accordingly. On the upper side of the upper tool contour shell 2, a shot hole 8 is formed, via which the core molding material and, if necessary, also the binder can be introduced into the core shooting tool 1. From the left and from the right, two C-shaped clamps 5 engage laterally around both halves of the core shooting tool 1 and hold them against each other under a certain pretension.

A core shooting process in a core shooting tool 1 closed with a clamp 5 (not shown) is shown in FIG. 4 . The core shooting tool 1 is supported on a carrier plate 7. Via this carrier plate 7, the core shooting tool 1 can also be moved into and out of the core shooting machine. Above the core shooting tool 1, a vertically adjustable shooting head 6 is shown, which docks with a corresponding nozzle to the shot hole 8 in order to inject the necessary material such as sand and/or binder into the cavity 4 of the core shooting tool 1. The closing of the tool by means of clamps 5 or a toggle device can already take place outside the machine. Alternatively, both tool contour shells 2, 3 can be introduced separately into the machine and only closed and clamped together in the machine. The core shooting tool is positioned below the shooting head 6 by moving the carrier plate 7 horizontally, the shooting head 6 then moves vertically into the shot hole 8 and shoots sand and/or binder into the cavity 4.

Subsequently, the core shooting tool 1 together with the capping device 5 and the enclosed sand binder mixture are transferred from the core shooting machine to a curing furnace 9, which is shown in FIG. 5 . In the curing furnace 9, the core shooting tool 1 is heated to a predetermined temperature over a predetermined period of time so that the core can cure.

FIG. 6 shows schematically the sequence of the core shooting method according to the invention for the production of cores with simultaneous curing process. The course of a core shooting tool 1 through the process is shown. First, a lower and an upper tool contour shell 2, 3 are placed on top of each other in such a way that they form a geometrically adapted cavity 4 inside. The tool contour shells 2, 3 are then fixed to each other by means of clamps 5 under a predetermined preload. The core shooting tool 1 prepared in this way is then transferred to the core shooting machine, in which sand and/or binder is injected into the cavity 4 by means of a shooting head 6 via the shot hole 8. The core shooting tool 1 is then transferred together with the enclosed sand/binder mixture to the curing furnace 9 for curing. After the core has cured, the core shooting tool 1 is removed from the curing furnace 9 and both tool contour shells 2,3 are separated from each other so that the core can be removed. The two tool contour shells 2, 3 are then transferred to a cleaning device 10, in which sand and binder residues are removed and the tool contour shells 2, 3 are returned to a condition suitable for shooting. Both mold contour shells 2, 3 are then prepared for the injection of a further core and the cycle starts again. Simultaneous to the one 1 shown, several other core shooting tools 1 are in the same process, for example 20, in order to achieve the highest possible utilization of the core shooting machine. A further core shooting tool 1 is transferred to the core shooting machine as soon as the previous core shooting tool 1 has left the machine and is transferred to the curing furnace 9. The curing furnace 9 is preferably a continuous furnace which receives the individual subsequent core shooting tools 1 in accordance with the cycle time of the core shooting machine.

FIG. 7 a shows an alternative embodiment of the invention in which a sand-binder mixture is not simultaneously injected into the cavity 4, but the binder is applied to the inner contour of each cavity half before the mold contour shells 2, 3 are closed. The shells are then closed and the core molding material is injected into the cavity 4 via the injection opening 8, as shown in FIG. 7 b.

FIGS. 8 a and 8 b show an embodiment of the invention in which the binder is introduced neither via the shot hole 8, nor by prior application to the cavity halves, but via a separate injector system 15, which is injected into the cavity 4 by means of several injector nozzles 13, either via the vent nozzles 12 or via additionally provided openings in one of the mold contour shells. In this embodiment, the sand is first injected into the cavity 4 via the shooting head 6 through the shot hole 8. Subsequently, the injection nozzles 13 of the injector system 15 are inserted into the cavity 4 through the associated holes and the binder is then injected into the injected sand.

FIG. 9 shows a further embodiment of the core shooting tool 1, in which the lower tool contour shell 3 and the upper tool contour shell 2 are designed in such a way that they together form an additional opening 16, via which access to the cavity 4 is provided from the outside of the core shooting tool 1. This opening 16 serves to accommodate a side shift 14, which is inserted laterally into the cavity 4 before the sand is shot into it and serves to form an undercut contour of the sand core.

The features of the invention disclosed in the foregoing description, in the figures as well as in the claims may be essential for the realization of the invention both individually and in any combination.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

1-16. (canceled)
 17. A core shooting method using a plurality of core shooting tools, each of which is adjustable between an open position and a closed position, wherein in the closed position the core shooting tools each form a hollow chamber geometrically adapted to a core to be shot, the method comprising the sequence of steps: a. Inserting a first core shooting tool into a core shooting machine; b. Injecting core molding material and a binder into the first core shooting tool; c. Ejecting the first core shooting tool from the core shooting machine; d. Curing of the core in the first core shooting tool; Repeating the previous steps with at least one further core shooting tool, wherein insertion of the further core shooting tool into the core shooting machine is carried out simultaneously with ejection of the previous core shooting tool from the core shooting machine or simultaneously with curing of the core in the previous core shooting tool, wherein inserting a first core shooting tool into a core shooting machine comprises inserting two tool contour shells having a wall thickness of less than 20 mm, and in that for curing the core in the first core shooting tool the core shooting tool is transferred into an infrared furnace.
 18. The core shooting method of claim 17, wherein prior to shooting core molding material and a binder into the first core shooting tool, preloading of binder onto the interior surfaces of the hollow chamber occurs.
 19. The core shooting method of claim 17, wherein step b. comprises: Injecting core molding material into the first core shooting tool and injecting binder into the injected core molding material.
 20. The core shooting method of claim 17, wherein step b. comprises: Injecting a core molding material and binder mixture into the core shooting tool.
 21. The core shooting method according to claim 17, wherein the process is a cold box process.
 22. The core shooting method according to claim 17, wherein the binder is an inorganic binder.
 23. The core shooting method according to claim 17, wherein the curing temperature when the core is cured is less than or equal to 110° C., preferably less than or equal to 100°, more preferably less than or equal to 90° C.
 24. The core shooting method according to claim 17, wherein, after the core has cured, the core shooting tool is opened and the cured core is removed.
 25. The core shooting method according to claim 24, wherein the core shooting tool is cleaned after removal of the core, reset to a shootable state, and subsequently reintroduced into the core shooting machine.
 26. The core shooting method according to claim 17, wherein the same geometrically adapted hollow chamber is formed in each of the plurality of core shooting tools.
 27. A core shooting device for carrying out the core shooting method according to claim 17, having a core shooting machine, a plurality of core shooting tools, and a curing furnace, wherein the core shooting tools each have a first tool contour shell and a second tool contour shell which can be moved back and forth between a closed position and an open position, wherein in the closed position a hollow chamber geometrically adapted to a core to be shot is formed in the core shooting tool, with at least one shot hole for shooting core molding material and/or binder into the hollow chamber, and with in each case at least one frame for moving the core shooting tools into and out of the core shooting machine, the frame having at least one horizontally and/or vertically supporting support element for absorbing forces acting on the tool contour shells, wherein the curing furnace is an infrared furnace, and wherein the tool contour shells each have a wall thickness of less than 20 mm.
 28. The core shooting device of claim 27, wherein the core shooting tool further comprises at least one closing element for automated closure, in particular at least two closing clamps, which holds the tool contour shells in the closed position.
 29. The core shooting device of claim 27, wherein the tool contour shells each have a wall thickness of less than 10 mm, more preferably less than 5 mm.
 30. The core shooting device of claim 27, wherein the tool contour shells are formed substantially of plastic.
 31. The core shooting device according to claim 27, wherein a vent nozzle is provided on at least one of the tool contour shells. 